(a) Field of the Invention
The present invention relates to an organic light emitting device.
(b) Description of the Related Art
Recently, liquid crystal displays (“LCDs”) are being substituted for cathode ray tubes (“CRTs”) wherever a lighter and/or thinner display is desired.
However, LCDs have many problems. One of which is that LCDs require a separate backlight as a light emitting and receiving element, and in addition LCDs have a slow response speed and a narrow-viewing angle.
As a display device for solving these problems, an organic light emitting device (“OLED”) has come into the spotlight in recent times.
An OLED includes two electrodes with an emitting layer interposed therebetween. In an OLED, electrons are injected from one electrode and holes are injected from the other electrode and both electrons and holes are recombined in the emitting layer to form excitons. Light is emitted when the excitons release energy.
Since the OLED is a self-emission type of display in which a separate light source is not necessary, it has the advantages of low power consumption, a good response speed, a wide viewing angle, and a good contrast ratio.
The OLED includes a plurality of pixels including, for example, a red pixel, a blue pixel, and a green pixel and can produce a full color display by combining the light emitted by these pixels. In one arrangement, each of the differently colored pixels uses a light emitting layer composed of a different material to produce emitted light of different wavelengths (and therefore different colors).
Alternatively, the OLED may include pixels wherein each pixel emits only a white light. One method of producing such a pixel is to include a red, blue and green light emitting layer within a single pixel, which thereby emits a white light. In such an alternative configuration, an additional color filter layer having red, blue and green components must be added in order to produce a color display.
However, the OLED has different light emission efficiencies depending on the light emitting material used to produce the variously colored pixels. In other words, the same amount of applied voltage may produce a different amount of emitted light in each of the differently colored pixels. In this case, among red, green, and blue colors, the color having low emission efficiency does not have a predetermined color coordinate. In addition, the emission efficiency of a white light generated by a combination of the red, green, and blue colors is reduced due to the inclusion of a color having a light emitting layer with a low emission efficiency.